"A viewer in Pennsylvania who is watching an average amount of television would see pro-Romney ads 50 times in the last five days of the campaign," says Alison Dagnes, a political science professor at Shippensburg University.
Dagnes says Pennsylvania is unusual. Its political influence depends on the race.
"We have gone from Republican to Democrat to Republican to Democrat when it comes to electing our governors and the same thing essentially goes for our state house and state senate."
But, in the last five presidential elections the state has leaned left. In 2008, President Obama won Pennsylvania by 11 points.
"What we may see this year is an Obama victory but with smaller numbers in-between," says Dagnes.
Both campaigns have already mobilized legal teams in battleground Florida, where a victory may be too close to call.
"We may see automatic recounts triggered. We may see legal challenges made, and as a result we may not have a winner [Tuesday] night. We may have to wait several weeks."